Throughout the disclosure, including in the claims, the expression "processor" denotes any device within the broad class of data recording apparatus, data processing apparatus, and apparatus for providing control signals to a peripheral device (such as a CRT or other video format display device). Examples of such "processors" include desktop computers, networks of computers, and devices such as printers, magnetic disk storage devices, and digital electronic memory banks.
Throughout the disclosure, including in the claims, the expression "display device" denotes any text or image display device within the broad class of CRT based computer displays, video monitors, and the like, which are controlled by an internal digital processor. Operation of a display device is typically controlled by sending control data (such as configuration, adjustment, or alignment data) to the internal digital processor from an external processor, and the display device is typically capable of sending status data (including information about text or image data stored in the display device) to the external processor.
Alignment and adjustment data must be transmitted to and from a display device during manufacture or repair of the device, and occasionally during normal operation to adjust the display to produce a best quality image. Alignment data is not itself displayed. Depending on the display device design, usually only a small amount of digital alignment and adjustment data must be transmitted to the display device, and only a smaller amount of status data must be transmitted from the display device, to accomplish alignment or adjustment or both.
In one type of conventional display system, interactive adjustment data (including status and control data) are transferred over a digital communication path (separate from the display signal channel, which can be a color analog video channel) between an internal processor within a display device and an external processor. In such systems, the communication path is implemented by traditional computer communication hardware, such as a serial port in the external processor, a serial port in the display device, and a cable connecting the serial ports. However, inclusion of a serial port in the display device adds cost, because a connector and an interface chip are required, and supporting interface logic and additional power supply capacity are needed to operate the interface hardware.
It would be desirable to communicate such control and status data to and from a display device in a less expensive manner, without the need for special communications hardware such as a serial port and associated hardware.
It is conventional to encode a variety of information in video format, for example, in computer disk back up systems using consumer video recorders, instrumentation recorders using video recording formats, video-text information distribution systems, and authorization systems for subscriber television cable systems. However, until the present invention, control data for a display device has not been encoded in a video signal that is transmitted to the display device.